Frenzel FM-DP1 Tube Preamp

For five decades after he built his first guitar amp in 1952, Jim Frenzel designed tube and solidstate equipment for the military, FAA, and Texas Instruments. But it wasn’t until 2001, after his retirement, that he returned to tube guitar amps.

Frenzel’s philosophy is pretty straightforward; he designs and builds amps that easily dial up “tones you know” while allowing room for customization. One prime example is his FM-DP1 Tube Preamp.

A dual-channel dedicated guitar preamp for stage and studio use, the FM-DP1 is part of Frenzel’s Inspired line and is designed to give classic tones inspired by vintage Fender- and Marshall-style amps with some of Frenzel’s modifications.

The preamp uses two 12AX7s with DC on the filaments to control noise. The first 12AX7 is wired as a dual-input preamp for the channels, labeled Type F and Type M. Each is then controlled by individual Gain controls. The second 12AX7 is wired as a common-voltage-type amplifier with a cathode follower to drive the tone stack. The three-band tone stack has knobs for Bass, Mid, and Treble, with an optional push/pull Deep Bass Boost switch (on the Bass knob) to capture more of a classic Bassman vibe. Add in a Master Gain knob and you have the basics for a very usable workhorse preamp.

The FM-DP1 is like all of Frenzel’s products in that it is hand-wired, with no printed circuit boards. A feature common in higher-priced boutique amps, here it’s a surprising addition. Another cool design feature is a trim knob on the rear panel for setting output gains.

Also cool is how the signal goes into the FM-DP1 as high-impedance and comes out low-impedance, which makes the preamp usable as an extra gain stage, to overdrive an amp, or as the front end of a recording rig.

Using a single-coil guitar plugged into the Type F input and with the FM-DP1 running into the power-amp section of a 40-watt open-back combo driving a Celestion Vintage 30, the tone was instantly recognizable – classic Bassman vibe, with an overall warmth that made notes full with just-right midrange snap. The Treble control dialed in pleasant-but-not-overbearing top-end. Players looking for a chimier tone may need to crank the Treble to get that extra bite from the Type F channel. Fortunately, it doesn’t produce much hiss when dimed.

Jazz and bass players should take notice of the optional Deep Bass Boost switch that can be added to the Bass control. In Type F, this helps the Frenzel morph into a full-figured rig with lots of low-end. Hollowbody guitars sound thunderous in the neck position, and basses capture the sort of old-school bass tone still used in numerous applications. There is no extra charge for this upgrade, so it’s a no-brainer.

The multiple personality of the FM-DP1 is made complete with the addition of the Type M channel. Here, the EQ section and voicing take on a new personality; mids and highs shimmer and the Gain control helps push the Frenzel to searing rock tones worthy of any stage. Humbucker-loaded solidbodies, in particular, take on the mass and girth of a classic amp.

Other than the lack of a LED power indicator, there’s little to complain about with the Frenzel FM-DP1. Its stripped-to-the-essentials, open-chassis design is great for dialing up the sounds of classic amps, for the same cost as certain boutique pedals.